Subject: + mm-hotplug-remove-stop_machine-from-try_offline_node.patch added to -mm tree
To: toshi.kani@xxxxxx,isimatu.yasuaki@xxxxxxxxxxxxxx,kamezawa.hiroyu@xxxxxxxxxxxxxx,kosaki.motohiro@xxxxxxxxxxxxxx,liwanp@xxxxxxxxxxxxxxxxxx,rafael.j.wysocki@xxxxxxxxx,tangchen@xxxxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Wed, 14 Aug 2013 15:50:19 -0700
The patch titled
Subject: mm/hotplug: remove stop_machine() from try_offline_node()
has been added to the -mm tree. Its filename is
mm-hotplug-remove-stop_machine-from-try_offline_node.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-hotplug-remove-stop_machine-from-try_offline_node.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-hotplug-remove-stop_machine-from-try_offline_node.patch
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------------------------------------------------------
From: Toshi Kani <toshi.kani@xxxxxx>
Subject: mm/hotplug: remove stop_machine() from try_offline_node()
lock_device_hotplug() serializes hotplug & online/offline operations. The
lock is held in common sysfs online/offline interfaces and ACPI hotplug
code paths.
try_offline_node() off-lines a node if all memory sections and cpus are
removed on the node. It is called from acpi_processor_remove() and
acpi_memory_remove_memory()->remove_memory() paths, both of which are in
the ACPI hotplug code.
try_offline_node() calls stop_machine() to stop all cpus while checking
all cpu status with the assumption that the caller is not protected from
CPU hotplug or CPU online/offline operations. However, the caller is
always serialized with lock_device_hotplug(). Also, the code needs to be
properly serialized with a lock, not by stopping all cpus at a random
place with stop_machine().
This patch removes the use of stop_machine() in try_offline_node() and
adds comments to try_offline_node() and remove_memory() that
lock_device_hotplug() is required.
Signed-off-by: Toshi Kani <toshi.kani@xxxxxx>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Tang Chen <tangchen@xxxxxxxxxxxxxx>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
Cc: Wanpeng Li <liwanp@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory_hotplug.c | 31 ++++++++++++++++++++++---------
1 file changed, 22 insertions(+), 9 deletions(-)
diff -puN mm/memory_hotplug.c~mm-hotplug-remove-stop_machine-from-try_offline_node mm/memory_hotplug.c
--- a/mm/memory_hotplug.c~mm-hotplug-remove-stop_machine-from-try_offline_node
+++ a/mm/memory_hotplug.c
@@ -1694,9 +1694,8 @@ static int is_memblock_offlined_cb(struc
return ret;
}
-static int check_cpu_on_node(void *data)
+static int check_cpu_on_node(pg_data_t *pgdat)
{
- struct pglist_data *pgdat = data;
int cpu;
for_each_present_cpu(cpu) {
@@ -1711,10 +1710,9 @@ static int check_cpu_on_node(void *data)
return 0;
}
-static void unmap_cpu_on_node(void *data)
+static void unmap_cpu_on_node(pg_data_t *pgdat)
{
#ifdef CONFIG_ACPI_NUMA
- struct pglist_data *pgdat = data;
int cpu;
for_each_possible_cpu(cpu)
@@ -1723,10 +1721,11 @@ static void unmap_cpu_on_node(void *data
#endif
}
-static int check_and_unmap_cpu_on_node(void *data)
+static int check_and_unmap_cpu_on_node(pg_data_t *pgdat)
{
- int ret = check_cpu_on_node(data);
+ int ret;
+ ret = check_cpu_on_node(pgdat);
if (ret)
return ret;
@@ -1735,11 +1734,18 @@ static int check_and_unmap_cpu_on_node(v
* the cpu_to_node() now.
*/
- unmap_cpu_on_node(data);
+ unmap_cpu_on_node(pgdat);
return 0;
}
-/* offline the node if all memory sections of this node are removed */
+/**
+ * try_offline_node
+ *
+ * Offline a node if all memory sections and cpus of the node are removed.
+ *
+ * NOTE: The caller must call lock_device_hotplug() to serialize hotplug
+ * and online/offline operations before this call.
+ */
void try_offline_node(int nid)
{
pg_data_t *pgdat = NODE_DATA(nid);
@@ -1765,7 +1771,7 @@ void try_offline_node(int nid)
return;
}
- if (stop_machine(check_and_unmap_cpu_on_node, pgdat, NULL))
+ if (check_and_unmap_cpu_on_node(pgdat))
return;
/*
@@ -1802,6 +1808,13 @@ void try_offline_node(int nid)
}
EXPORT_SYMBOL(try_offline_node);
+/**
+ * remove_memory
+ *
+ * NOTE: The caller must call lock_device_hotplug() to serialize hotplug
+ * and online/offline operations before this call, as required by
+ * try_offline_node().
+ */
void __ref remove_memory(int nid, u64 start, u64 size)
{
int ret;
_
Patches currently in -mm which might be from toshi.kani@xxxxxx are
mm-hotplug-remove-unnecessary-bug_on-in-__offline_pages.patch
mm-hotplug-verify-hotplug-memory-range.patch
mm-hotplug-remove-stop_machine-from-try_offline_node.patch
linux-next.patch
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